Oscillation generator



NOV. 4-, 1930. GREEN 1,780,229 H 050 ILLATION GENERATOR Filed Sept. 10, 1927 INVEN TOR. BI Green A TTORNEY Patented Nov. 4, 1930 UNITED STATES- PATENT OFFICE ESTIIJL I. GREEN, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEEV YORK OSCILLATION GENERATOR Application filed September 10, 1927. Serial No. 218,774.

This invention relates to oscillation generators, and more particularly to generators having means for maintaining substantially constant the frequency of the sustained oscillations.

A pieZo-electric device may be employed to control the frequency of oscillations generated by, for example, space discharge tube oscillators. Such a device may be cut from a substance such as quartz, and it is a fact that such a device responds to a plurality of frequencies with various degrees of activity. There is one of these frequencies at which the device exhibits its greatest response, this frequency being generally known as the natural frequency of the device.

In accordance with this invention, it is proposed to simultaneously set a pieZ'o-electric device into vibration at a plurality of frequencies and to utilize this device for maintaining the frequency of oscillations of, for example, an oscillation generator of the vacuum tube type constant within very narrow limits in accordance with a frequency derived from two or more of the vibratory periods of the device. Thus, if a piezo-electric device be found to have two vibratory periods of, for example, 1100 kilocycles and 1095 kilocycles, it is proposed to use the beat period of five kilocycles in order to control oscillations in a vacuum tube oscillation generator'thereat. Yet, if there are a greater number of vibratory periods for a particular piezo-electric device, it is proposed to utilize some of the various vibratory periods in suitable combination to provide a stabilizing medium for sustained oscillations of an oscillation generator.

Accordingly, it is one of the objects of this invention to unite or combine any two or more of the vibratory periods of a piezoelectric device in order to produce some desired resultant period, constant in its vibrations within exceedingly narrow limits.

It is another object of this invention to relate a piezo-electric body capable of vibrating at a plurality of frequencies to an oscillator so as to control the frequency of sustained oscillations in accordance withthe beat period corresponding to certain selected vibrations of said body.

t is a further object of this invention to provide a piezo-electric structure capable of vibrating simultaneously at a plurality of frequencies and to change one or more of these frequencies of vibration with respect to a selected frequency of vibration of said structure.

And it is a further object of this invention to provide a piezoelectric structure capable of vibrating simultaneously at a plurality of frequencies and to further provide means for changing the amplitude of the vibrations at one of these frequencies with respect to the amplitude of vibrations of another of these frequencies.

lVhile this invention will be pointed out with particularity in the appended claims, the invention itself, both as to its further objects and features, will be better understood in connection With the detailed description hereinafter following, when read in connection with the accompanying drawing showing one embodiment of the invention merely for the purpose of illustration.

Referring to the drawing, there is shown a piezoelectric device associated with the circuits of an electron tube arrangement so that sustained oscillations, controlled as to frequency by the piezoelectric device, may be generated. The oscillating circuit includes a thermionic tube V having a filament, a grid and a plate, the filament being heated to an electron-emitting temperature by battery B T 1e grid is connected to the filament of this vacuum tube through a resistance R and a battery B battery B aiding to maintain the grid of tube V at a suitable potential with respect to its filament. The necessary operating potential for the plate of tube V is provided-by a battery B battery B being connected to the plate of tube V through a choke coil W1.

The input circuit of the vacuum tube V includes a winding and a condenser C these being tuned to give oscillations of the desired frequency. The period of the oscillations may be changed by varying the magnitude of the capacity of condenser C or the magnitude of the inductance of winding'w or both, as found desirable. A circuit including the adjustable resistance B a winding adjustable condenser 1V and a condenser C permits the transmission of energy from the output circuit of the vacuum tube V: to its input circuit. Thus, energy is fed from the output circuit of tube V to its input circuit, due particularly to the inductive relationship existing between windings N and W The amplitude of the 7 current transmitted to the input circuit may be controlled by manipulationofthe movable contact of the resistance R Condenser G prevents the applica'tionof the potential of battery B tothe input circuit, and particularly to the grid of vacuum tube V. The outvacuum tube V through a condenser C of adjustable capacity, and a winding W of adjustable inductance. Terminal P is con nected to the grid of vacuum tube V- through a variable resistance R3! 7 The piezo-electric'structure or device PE may set up vibrations oftwo or more frequencies. Vibrations of one frequency may be impressed across the terminals or conductors P and P while vibrations of another frequency may be impressed across terminals or conductors P and P Condenser C, may

be changed in capacity, or winding W may.

be changed in inductance, or both may be changed, to provide a change'in the vibratory period of the piezo-electric' device PE established between terminals or electrodes P and P Such a change may often be made only between narrow limits of frequency. It is to be understood, however, that while inductance andcapacity have been shown in.

series relationship with the pi-ezo-electric device toproduce a variation in one of its vibratory periods, shunt inductance and capacity maybe similarly employed, or a variable air-gap may be provided for a similar purpose, within the scope of this invention.

Vibrations of another frequency may be established between terminals or electrodes P andP j By changing the magnitude of resistance R the amplitude of these vibrations may be changed, as desired, with re spect to the amplitude of the vibrations established between electrodes P and P Obviously, by decreasing the magnitude of resistance R the amplitude of the vibrations between electrodes P and-P are increased, and,

Tconversely, by increasingthe magnitude of resistance R these vibrations are decreased in amplitude,

In this arrangement,oscillations are sustained, the frequency of which is maintained constant in accordance with the beat period corresponding to selected vibrations of the piezo-electric device. As mentioned hereinabove, if one of'the frequencies of response of the piezo-electric device is 1100 kilocycles, and ifanother frequency'of response is 1095 kilocycles, the vacuum tube oscillation gen:v

erator may be caused to sustain oscillations at the beat period of 5 kilocycles. It is to be understood, however, that while only two of the vibratory periods of a piezo-electric device or structure have been combined for illustration in the production of oscillations corresponding to their beat period, three or more vibratory periods of 'a piezo-electric structure or device may be similarly'combinedwithin the scope of this invention. It is to be further understood that while two of theresponse frequencies of a piezo-electric structure or device have been combined to maintain sustained oscillations constant-at a frequency corresponding to their difierence, it is within the scope of this invention to maintain sustained oscillations constant at frequencies corresponding to their sum or to the sum of any three or more of the response frequencies of any piezo-electric structure or device. I r Heretofore, a piezo-electric device has been employed to controland stabilize oscillations of an oscillation generator in accordance with a single selected frequency of the device, 'whichwas of exceedingly high order. The vacuum tube oscillating generator shown herein is capable of sustaining oscillations at a considerably lower frequency, which may be in the audible range, the sustained oscillations being maintained constant in accordance with the frequency corresponding to the difference between two of'the response he quencies of the piezoelectric device which are above the audible range.

The tuned circuit comprising winding W and condenser C may, if desired, be replaced by a pair of tuned circuits in series relationship, 'each of suitable inductance andcapacity, one tuned circuit corresponding to. one of the vibratory periods of the piezoelectric .de-

vice, and the other tuned circuit correspond ing. to another vibratory period of thepiezoelectric device, within the scope ofthis in- V vention.

While thisinvention has been pointed out inone particular embodiment merelyfor the purpose of illustration, it is to be distinctly understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims. What is "claimed is: 1. The combination of a piezoelectric de- 7 Vice capable of vibrating simultaneously in a plurality of modes at differentfrequencies, said piezo-electric device having a pair of electrodes for its vibration in each mode, and means for uniting selected frequencies of vibration of said pieZo-electric device to produce a substantially difierent frequency of vibration.

2. The combination of a piezo-electric device capable of vibrating naturally at a plurality of frequencies simultaneously, resistive means for controlling the amplitude of vibration of one of said frequencies, and means for changing by a predetermined amount the frequency of another of the vibrations of said piezo-electric device with respect the frequency of the vibrations being controlled as to amplitude.

8. The combination of a piezoelectric device having four electrodes, a r sistance of adjustable magnitude in series with two of said electrodes to control the amplitude of the current of one of the frequencies impressed therebetween, and a reactance of adjustable magnitude in series with the other two of said electrodes to control the frequency of the other current impressed therebetween.

l. The combination of a p'eZo-electric device having two pairs of electrodes between which independent vibrations of different frequencies may take place, a circuit including an adjustable resistance in ser' 1 "h one pair of said electrodes, and a circuit including an adjustable reactance in series with the other pair of said electrodes.

5. The combination of a pieZo-electric device capable of vibrating naturally at a pair of frequencies simultaneously, means includ ing variable inductance and variable capacity in series relationship to change one of said frequencies of vibration of the piezoelectric device by a predetermined amount with respect to the other said frequencies, and an oscillator controlled as to frequency in accordance with the beat period of the resultant pair of frequencies.

6. The combination of a piezo-electric device capable of vibrating naturally at a pair of frequencies simultaneously, reactive means comprising variable inductance and variable capacity in series relationship to change one of said frequencies of vibration of said device by a predetermined amount with respect to said other frequency of vibration, means for combining the resultant frequencies so as to produce vibrations of an audible frequency, a vacuum tube oscillator, and means to control the oscillations of said vacuum tube oscillator in accordance with said audible frequency.

7. The combination of a piezo-electric structure having two natural vibratory periods, both periods being inaudible though differing from each other by an audible amount, means including variable inductance and variable capacity in series relationship for changing one of the vibratory periods of said piezo-electric structure with respect to the other by any predetermined amount, and means for combining the resultant frequencies in order to produce the audible frequency.

8. The combination of a piezo-electric structure having two natural vibratory periods which differ from each other by an audible frequency, resistive means for varying the amplitude of one of the vibrations by a predetermined amount with respect to the amplitude of the other of the vibrations, means for combining these frequencies to produce said audible frequency, and a vacuum tube system sustaining oscillations which may be maintained constant in frequency in accordance with said audible frequency.

9. The combination of a piezoelectric body having dimensions permit-ting its vibration in two modes simultaneously at two distinct frequencies corresponding to its physical dimensions, means for changing the amplitude of one of the vibrations of the piezoelectric body by a predetermined amount with respect to the amplitude of the other of the vibrations, means for varying the frequency of one of the vibrations of the piezoelectric body with respect to the other of the vibrations, and a work circuit controlled by said body at a frequency equal to the difference between the resultant frequencies of vibration.

in testimony whereof, I have signed my name to this specification this 7th day of September, 1927.

ESTILL I. GREEV.

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